UK PARTICIPATION IN EUROPEAN ENERGY INSTITUTIONS

Introduction

The United Kingdom’s participation in European energy institutions changed fundamentally after Brexit. The UK left the European Union on 31 January 2020 and ceased participation in the EU internal energy market at the end of the transition period on 31 December 2020. Nevertheless, geographical interconnection, electricity trading, gas infrastructure, offshore renewable development and energy-security concerns continue to require extensive UK-European cooperation. The present framework is based primarily on the EU-UK Trade and Cooperation Agreement (TCA), bilateral agreements and specialised cooperation with European energy bodies. The TCA Energy Title has been extended until 31 March 2027, while the UK and EU are also pursuing negotiations concerning possible UK participation in the EU internal electricity market.

EU-UK Trade and Cooperation Agreement

Title VIII of the TCA establishes the principal legal framework for UK-EU energy cooperation. It addresses electricity and gas trading, energy security, interconnectors, renewable energy and regulatory cooperation. The Specialised Committee on Energy supervises implementation, conducts technical discussions and facilitates information exchange between the UK and EU.

The framework recognises that the British and European electricity systems remain physically interconnected. However, Great Britain is currently outside the EU internal electricity market and does not participate in ordinary EU market-coupling arrangements on the same basis as Member States. Northern Ireland occupies a distinct position because the Single Electricity Market with Ireland continues under arrangements associated with the Withdrawal Agreement.

Cooperation with ACER

The Agency for the Cooperation of Energy Regulators (ACER) coordinates national energy regulators within the EU. After Brexit, Ofgem no longer participates in ACER as the regulator of an EU Member State.

Under the TCA, however, cooperation between ACER and the UK regulatory authorities is expressly contemplated. A 2024 decision of the Specialised Committee established guidance for administrative arrangements between ACER and GEMA/Ofgem and the Utility Regulator for Northern Ireland. Cooperation may cover electricity and gas markets, network access, market-abuse prevention, security of supply, infrastructure planning and interconnection. Significantly, the arrangements must preserve decision-making autonomy and cannot give UK regulators a status equivalent to membership of ACER.

ENTSO-E and ENTSOG Cooperation

The TCA also requires cooperation between UK transmission system operators and the European Network of Transmission System Operators for Electricity (ENTSO-E) and the equivalent gas organisation, ENTSOG.

The purpose is to facilitate technical coordination, network planning, security of supply, interconnector management and efficient cross-border energy flows. The Specialised Committee adopted guidance in 2024 encouraging effective working arrangements between these European organisations and UK transmission-system operators.

North Seas Energy Cooperation

The UK also participates in cooperation with the North Seas Energy Cooperation (NSEC) under a Memorandum of Understanding signed in December 2022. This arrangement supports offshore wind, offshore grids, interconnectors and hybrid projects combining renewable generation with cross-border transmission.

The arrangement implements Article 321 of the TCA and permits the UK to work with neighbouring European states and the European Commission without restoring full EU membership. North Seas cooperation is particularly important for coordinated offshore renewable infrastructure and electricity interconnection.

Future Internal Electricity Market Participation

UK-European institutional integration may deepen further. Following the 19 May 2025 UK-EU Summit, both sides agreed to explore UK participation in EU electricity trading platforms. Exploratory discussions concluded in December 2025 that the parties should work toward a specific EU-UK Electricity Agreement concerning UK participation in the EU internal electricity market. By February 2026, both sides confirmed that detailed negotiations were being pursued.

Case Law: R (Miller) v Secretary of State for Exiting the European Union [2017] UKSC 5

Facts: The Government proposed using prerogative powers to notify withdrawal from the EU under Article 50 TEU.

Legal Issue: Whether ministers could initiate withdrawal without parliamentary authorisation.

Judgment: The Supreme Court held that an Act of Parliament was required.

Legal Principle/Ratio: Ministers cannot use prerogative powers to alter domestic law and remove statutory rights created through Parliament.

Significance: Miller explains the constitutional foundation of the UK's withdrawal from EU institutions, including the institutional structures governing European energy markets.

Case Law: R (SSE Generation Ltd) v Competition and Markets Authority [2022] EWCA Civ 1472

Facts: SSE challenged electricity transmission charging decisions involving GEMA, the CMA and National Grid ESO under rules substantially derived from EU electricity legislation.

Legal Issue: The case concerned interpretation and application of electricity transmission charging requirements following Brexit.

Judgment: The Court of Appeal examined the continuing domestic effect of EU-derived electricity rules and stressed the regulator's duty to act lawfully.

Legal Principle/Ratio: EU-derived energy rules preserved in domestic law can continue to govern electricity regulation after withdrawal, although they operate through the UK legal order.

Significance: The case demonstrates the continuing practical connection between UK electricity regulation and European market principles.

Conclusion

UK participation in European energy institutions is therefore based on structured cooperation rather than ordinary EU membership. Through the TCA, ACER cooperation, ENTSO-E and ENTSOG arrangements, NSEC participation and prospective electricity-market negotiations, the UK remains closely connected with European energy governance while retaining separate regulatory decision-making authority.